Infrared sensing device

Abstract

A meniscus lens has a dome shape and has a first surface facing a lens array and a second surface facing an infrared sensing element. The meniscus lens has a central portion and a peripheral portion. The central portion includes a top point that is an intersection between the optical axis of the meniscus lens and the first surface. The peripheral portion includes an end of the first surface of the meniscus lens. With respect to the central portion of the meniscus lens, an aplanatic point of the first surface is located at the focus of the lens array. With respect to the peripheral portion of the meniscus lens, an aplanatic point of the second surface is located at the focus of the lens array.

The invention claimed is: 
     
       1. An infrared sensing device comprising:
 an infrared sensing element; 
 a lens array including multiple lenses, arranged to intersect with an optical axis of the infrared sensing element, and having a focus on the same side as the infrared sensing element; and 
 a meniscus lens having a dome shape, the meniscus lens being arranged between the lens array and the infrared sensing element and having a first surface facing the lens array and a second surface facing the infrared sensing element, 
 the meniscus lens having 
 a central portion including: a top point that is an intersection between the optical axis of the meniscus lens and the first surface; and an intersection between the optical axis of the meniscus lens and the second surface; and 
 a peripheral portion including an end of the first surface of the meniscus lens and an end of the second surface of the meniscus lens, 
 an aplanatic point of the first surface being located, with respect to the central portion of the meniscus lens, at the focus of the lens array, 
 an aplanatic point of the second surface being located, with respect to the peripheral portion of the meniscus lens, at the focus of the lens array. 
 
     
     
       2. The infrared sensing device of  claim 1 , wherein
 the meniscus lens is a Fresnel lens having, on the second surface, a plurality of lens surfaces arranged concentrically around the optical axis of the meniscus lens, 
 the first surface has a larger radius of curvature in the peripheral portion than in the central portion, and 
 each of the plurality of lens surfaces is tilted such that as a distance from the top point increases in a direction parallel to the optical axis of the meniscus lens, a distance from the optical axis to the lens surface also increases accordingly, or 
 each of the plurality of lens surfaces is parallel to the optical axis of the meniscus lens. 
 
     
     
       3. The infrared sensing device of  claim 1 , wherein
 the meniscus lens has, on the second surface, a plurality of lens surfaces arranged concentrically around the optical axis of the meniscus lens with respect to the central portion, and also has, on the first surface, another plurality of lens surfaces arranged concentrically around the optical axis of the meniscus lens with respect to the peripheral portion, 
 each of the plurality of lens surfaces on the second surface is tilted such that as a distance from the top point increases in a direction parallel to the optical axis of the meniscus lens, a distance from the optical axis to the lens surface also increases accordingly, or 
 each of the plurality of lens surfaces on the second surface is parallel to the optical axis of the meniscus lens, and 
 each of the plurality of lens surfaces on the first surface is tilted such that as the distance from the top point increases in the direction parallel to the optical axis of the meniscus lens, a distance from the optical axis to the lens surface also increases accordingly. 
 
     
     
       4. The infrared sensing device of  claim 1 , wherein
 materials for the lens array include polyethylene, and 
 materials for the meniscus lens also include polyethylene. 
 
     
     
       5. The infrared sensing device of  claim 1 , comprising:
 a first member including the lens array; and 
 a second member including the meniscus lens, wherein 
 the first member and the second member are integrated together. 
 
     
     
       6. The infrared sensing device of  claim 5 , wherein
 one member selected from the group consisting of the first member and the second member has a plurality of hooks, and the other member selected from the group consisting of the first member and the second member has a plurality of holes corresponding one to one to the plurality of hooks, and 
 each of the plurality of hooks passes through a corresponding one of the plurality of holes and is hooked on a region surrounding the corresponding hole to make the first member and the second member integrated together. 
 
     
     
       7. The infrared sensing device of  claim 6 , further comprising a package that houses the infrared sensing element, wherein
 the package includes a window member intersecting with the optical axis of the infrared sensing element and configured to transmit an infrared ray, 
 the second member includes: 
 a cylindrical portion surrounding the package; and 
 a plurality of ribs spaced apart from each other along a circumference of the cylindrical portion and protruding from an inner peripheral surface of the cylindrical portion, and 
 the plurality of ribs are in contact with a side surface of the package. 
 
     
     
       8. The infrared sensing device of  claim 7 , wherein
 the second member includes a positioning protrusion protruding from the inner peripheral surface of the cylindrical portion and abutting on one side, opposite from the meniscus lens, of the package. 
 
     
     
       9. The infrared sensing device of  claim 7 , wherein
 the package includes: 
 a package body housing the infrared sensing element and holding the window member; and 
 a projection protruding in such a direction as to intersect with the optical axis of the infrared sensing element from one end, opposite from the window member, of the package body, and 
 the cylindrical portion of the second member has a groove in which the projection is fitted on an end face opposite from the meniscus lens. 
 
     
     
       10. The infrared sensing device of  claim 1 , wherein
 the infrared sensing element is a pyroelectric element. 
 
     
     
       11. The infrared sensing device of  claim 2 , wherein
 materials for the lens array include polyethylene, and 
 materials for the meniscus lens also include polyethylene. 
 
     
     
       12. The infrared sensing device of  claim 3 , wherein
 materials for the lens array include polyethylene, and 
 materials for the meniscus lens also include polyethylene. 
 
     
     
       13. The infrared sensing device of  claim 2 , comprising:
 a first member including the lens array; and 
 a second member including the meniscus lens, wherein 
 the first member and the second member are integrated together. 
 
     
     
       14. The infrared sensing device of  claim 3 , comprising:
 a first member including the lens array; and 
 a second member including the meniscus lens, wherein 
 the first member and the second member are integrated together. 
 
     
     
       15. The infrared sensing device of  claim 4 , comprising:
 a first member including the lens array; and 
 a second member including the meniscus lens, wherein 
 the first member and the second member are integrated together. 
 
     
     
       16. The infrared sensing device of  claim 13 , wherein
 one member selected from the group consisting of the first member and the second member has a plurality of hooks, and the other member selected from the group consisting of the first member and the second member has a plurality of holes corresponding one to one to the plurality of hooks, and 
 each of the plurality of hooks passes through a corresponding one of the plurality of holes and is hooked on a region surrounding the corresponding hole to make the first member and the second member integrated together. 
 
     
     
       17. The infrared sensing device of  claim 14 , wherein
 one member selected from the group consisting of the first member and the second member has a plurality of hooks, and the other member selected from the group consisting of the first member and the second member has a plurality of holes corresponding one to one to the plurality of hooks, and 
 each of the plurality of hooks passes through a corresponding one of the plurality of holes and is hooked on a region surrounding the corresponding hole to make the first member and the second member integrated together. 
 
     
     
       18. The infrared sensing device of  claim 15 , wherein
 one member selected from the group consisting of the first member and the second member has a plurality of hooks, and the other member selected from the group consisting of the first member and the second member has a plurality of holes corresponding one to one to the plurality of hooks, and 
 each of the plurality of hooks passes through a corresponding one of the plurality of holes and is hooked on a region surrounding the corresponding hole to make the first member and the second member integrated together. 
 
     
     
       19. The infrared sensing device of  claim 16 , further comprising a package that houses the infrared sensing element, wherein
 the package includes a window member intersecting with the optical axis of the infrared sensing element and configured to transmit an infrared ray, 
 the second member includes: 
 a cylindrical portion surrounding the package; and 
 a plurality of ribs spaced apart from each other along a circumference of the cylindrical portion and protruding from an inner peripheral surface of the cylindrical portion, and 
 the plurality of ribs are in contact with a side surface of the package. 
 
     
     
       20. The infrared sensing device of  claim 17 , further comprising a package that houses the infrared sensing element, wherein
 the package includes a window member intersecting with the optical axis of the infrared sensing element and configured to transmit an infrared ray, 
 the second member includes: 
 a cylindrical portion surrounding the package; and 
 a plurality of ribs spaced apart from each other along a circumference of the cylindrical portion and protruding from an inner peripheral surface of the cylindrical portion, and 
 the plurality of ribs are in contact with a side surface of the package.